In a rotary machine such as a centrifugal compressor, an impeller (a bladed wheel) provided so as to be rotatable relative to a casing, is provided inside of the casing. The rotary machine rotates the impeller, thereby increasing the pressure of a fluid drawn in from the outside of the casing and discharging the fluid to the outside in a radial direction of a flow path in the impeller. In the rotary machine such as a centrifugal compressor, the shape of a blade which is provided in the impeller is optimized in order to attain improvement in performance.
For example, PTL 1 discloses a technique relating to the shape of such a blade. In this centrifugal compressor, the distributions of a blade angle on the tip side and a blade angle on the root side of the blade are defined. Specifically, the blade angle on the tip side of the blade is formed in a curved shape having an angle distribution in which the angle becomes a local maximum point before it reaches a middle portion along a flow path and becomes the minimum after the middle portion. On the other hand, the blade angle on the root side of the blade is formed in a curved shape having an angle distribution in which the angle becomes an angle smaller than the blade angle on the tip side of the blade at a fluid inflow port, and becomes a local maximum point larger than the blade angle on the tip side before it reaches a middle portion.